The preferred embodiment concerns a method and a device to sort pixel data in a print data stream.
In digital printing the image data are often supplied to the print group in the form of pixel data in a print data stream. Each pixel data contains the information to control one pixel. In black-and-white printing such a pixel data can comprise only a single bit. If the pixel data contains greyscale and/or color information, it can also comprise multiple bits. Pixel data with two bits, four bits or eight bits respectively are typical.
The pixel data in the print data stream are normally supplied to a printing device in the order with which they should be printed next to one another in a print line. For example, if the pixel data in the printing device are generated from a vector representation they are also typically arranged in this order in a print data stream.
However, there are also print groups that cannot process the pixel data in this order. For example, there are print heads for inkjet printing that have inkjet nozzles arranged in multiple rows. Within the rows the inkjet nozzles are respectively identically spaced apart from one another. The inkjet nozzles of the different rows are respectively arranged offset from one another. This offset is designed such that, when all rows of inkjet nozzles print the same line in a print line on a recording material, each nozzle is associated with a different pixel on this line of the recording material. The print line is any line that is printed transverse to the transport direction of the recording material. A line along a print row that has a thickness of one pixel is designated as a print line in the following. In other words, this means that the printing along the print line on a recording material is composed via the printing of all rows of inkjet nozzles of the print head. Since the inkjet nozzles are spaced identically from one another in the individual rows, their spacing is identical to the number of pixels in a line on the recording material, which corresponds to the number of rows. For example, if the print head has 16 rows of inkjet nozzles, within each row the inkjet nozzles are spaced 16 pixels apart from one another.
A Scalable Raster Architecture (SRA) print data controller that, among other things, is controlled by means of Field Programmable Gate Arrays (FPGAs) in which complex logics are integrated is described in “Digital printing—Technology and printing techniques of Océ digital printing presses”, 10th edition, October 2006, ISBN 3-00-001081-5, Chapter 9 “The SRA Controller”.
The company Xilinx, Inc., USA manufactures different FPGAs. Such FPGAs possess configurable memory ranges that are also designated as Distributed RAMs (see, for example, Virtex-5 FPGA, User Guide, UG190 (v5.2) Nov. 5, 2009, Pages 178 and 181). These memory ranges can be configured with the Xilinx CORE Generator software.